Large cranes have been known for a long time through public prior use. Working machines of this type are used, for example, to lift loads and, to satisfy complex operating sequences, have a large number of drives and assemblies, which may have a cumulative power of up to 1000 kW. The energy consumption and the emitted pollutants of a crane of this type are correspondingly high.
A load-lifting device is known from U.S. Pat. No. 7,554,278 B2, to Wegner-Donnelly et al., which uses recovered energy, which is released, for example, on lowering a load, for the energy supply of the device. U.S. Pat. No. 5,936,375 to Enoki discloses a method for storing and reusing energy for a load-lifting system. The energy storage is based on batteries, which, because of their limited storage capacity may be extended, for example, by a flywheel. This form of energy storage is complex and, because of the increased component number, is associated with higher energy losses.
The Liebherr patent DE 10 2007 046 696 A1 to Schneider discloses a hydraulic operated crane with hybrid capabilities. However, hydraulically operated cranes are difficult to control and determine in advance the amount of energy needed to operate the crane, and the methods taught for use in hydraulically operated cranes will not work for electrically operated cranes.